A boy in love with a girl continues to be in love with her and a girl in love with a boy continues to be in love with him, until and unless any external agent(brother or father of the girl) comes into play and breaks the legs of the boy.

Second law:

The rate of change of intensity of love of a girl towards a boy is directly proportional to his bank balance.

Third law:

The force applied while proposing a girl by a boy is equal and opposite to the force applied by the girl while using her sandals.

Universal law:

Love can neither be created nor be destroyed, it can only be transfered from one girlfriend to another girlfriend.